In a typical switching converter with feedforward compensation, the amplitude of a saw-tooth ramp signal in a pulse width modulator is varied in proportion to the supply voltage. Converters with feedforward compensation have good stability but low accuracy. To increase accuracy, an error amplifier is added which compares the output voltage with a reference voltage and provides a corrective signal. For a high accuracy, the analog control loop must have a high gain, with potential problems of stability. External compensation components may be required to ensure stability.
For applications in portable devices, switching converters should be small and cheap. Integrated CMOS circuits respond to both demands, but a requirement for external compensation components would compromise the inherent benefits of that technology.